A resistance compression network substantially decreases the variation in effective resistance seen by a tuned rf inverter as loading conditions change. Circuits can include resistance compression networks and rectifiers to form rf-to-dc converters having narrow-range resistive input characteristics.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A circuit comprising: first and second loads having equivalent resistances at a first frequency that vary in a substantially identical fashion over a range of at least 2:1; and a resistance compression network including: an input port; a first output port for coupling to the first load; a second output port for coupling to the second load; and a reactive network coupled to the first input port, the first output port, and the second output port, wherein at the first frequency an equivalent resistance of the compression network input port varies over a first ratio as equivalent resistances of the first and second loads vary together over a second ratio which is larger than the first ratio.
2. The circuit of claim 1 wherein the reactive network includes: a first reactive branch in series with the first load, and a second reactive branch in series with the second load, wherein the reactances of the first and second reactive branches are substantially equal in magnitude and opposite in sign at the first frequency.
3. The circuit of claim 2 wherein the reactive network further includes: a third reactive branch in parallel with the series connection of the first reactive branch and the first load, and a fourth reactive branch in parallel with the series connection of the second reactive branch and the second load, wherein the third and fourth reactive branches connect at a circuit node, wherein the reactances of the third and fourth reactive branches are substantially equal in magnitude and opposite in sign at the first frequency.
4. The circuit of claim 2 wherein a first terminal of the first reactive branch and a first terminal of the second reactive branch are each coupled to a first terminal of the input port, a second terminal of the first reactive branch is coupled to a first terminal of the first load, a second terminal of the second reactive branch is coupled to a first terminal of the second load, and a second terminal of the first load and a second terminal of the second load are each coupled to a second terminal of the input port.
5. The circuit of claim 1 wherein the reactive network further includes: a first reactive branch in parallel with the first load, and a second reactive branch in parallel with the second load, wherein the reactances of the first and second branches are substantially equal in magnitude and opposite in sign at the first frequency.
6. The circuit of claim 5 wherein the reactive network further includes: a third reactive branch in series with the parallel connection of the first reactive branch and the first load, and a fourth reactive branch in series with the parallel connection of the second reactive branch and the second load, wherein the reactances of the third and fourth reactive branches are substantially equal in magnitude and opposite in sign at the first frequency, wherein a first terminal of the third reactive branch and a first terminal of the fourth reactive branch are each coupled to a first terminal of the input port, and a second terminal of the first reactive branch, a second terminal of the first load, a second terminal of the second reactive branch and a second terminal of the second load are coupled to a second terminal of the input port.
7. The circuit of claim 5 wherein a first terminal of the first reactive branch and a first terminal of the first load are each coupled to a first terminal of the input port, a first terminal of the second reactive branch and a first terminal of the second load are each coupled to a second terminal of the input port, and a second terminal of the first reactive branch, a second terminal of the first load, a second terminal of the second reactive branch and a second terminal of the second load are coupled together.
8. The circuit of claim 1 , wherein the first load includes a rectifier.
9. The circuit of claim 8 , wherein the rectifier presents a voltage and current at the first frequency that are in phase.
10. The circuit according to claim 9 , further including an inverter coupled to the input port of the resistance compression network.
11. The circuit according to claim 1 , wherein the compression network includes a resonant tank circuit.
12. The circuit of claim 1 , wherein input characteristics of the first and second loads vary in a matched fashion as operating conditions change.
13. A circuit, comprising: an inverter circuit; a resistance compression network including an input port and first and second output ports, and a reactive network, the input port coupled to the inverter circuit; the reactive network coupled to the first input port and the first and second output ports; and a first rectifier coupled to the first output port and a second rectifier coupled to the second output port, wherein at a first frequency an equivalent resistance of the compression network input port varies over a first ratio as equivalent resistances of the first and second rectifiers vary together over a second ratio which is larger than the first ratio.
14. The circuit according to claim 13 , wherein the inverter is a resonant inverter and the compression network includes a resonant tank circuit.
15. The circuit according to claim 13 , wherein the first and second rectifiers provide a substantially resistive load at the first frequency.
16. The circuit according to claim 13 , wherein compression of the resistances of the first and second rectifiers is about a center value of impedance corresponding to a reactive component of the reactive network.
17. A method, comprising: coupling reactive elements to form a resistance compression network, the compression network having an input port and first and second output ports, the first output port being adapted for coupling to a first load and the second output port being adapted for coupling to a second load; wherein the first and second loads have equivalent resistances at a first frequency that vary in a substantially identical fashion over a range of at least 2:1; wherein at a first frequency an equivalent resistance of the compression network input port varies over a first ratio as equivalent resistances of the first and second loads vary together over a second ratio which is larger than the first ratio.
18. The method according to claim 17 , further including coupling a first reactive branch in series with the first load, and a second reactive branch in series with the second load, wherein the reactances of the first and second reactive branches are substantially equal in magnitude and opposite in sign at the first frequency.
19. The method according to claim 18 , further including coupling a third reactive branch in parallel with the series connection of the first reactive branch and the first load, and a fourth reactive branch in parallel with the series connection of the second reactive branch and the second load, wherein a node is formed at a connection of the third and fourth reactive branches wherein the reactances of the third and fourth reactive branches are substantially equal in magnitude and opposite in sign at the first frequency.
20. The method according to claim 18 , further including coupling a first terminal of the first reactive branch and a first terminal of the second reactive branch to a first terminal of the input port, coupling a second terminal of the first reactive branch to a first terminal of the first load, coupling a second terminal of the second reactive branch to a first terminal of the second load, and coupling a second terminal of the first load and a second terminal of the second load to a second terminal of the input port.
21. The method according to claim 17 , further including: coupling a first reactive branch in parallel with the first load, and a second reactive branch in parallel with the second load, wherein the reactances of the first and second branches are substantially equal in magnitude and opposite in sign at the first frequency.
22. The method of claim 21 , further including coupling a third reactive branch in series with the parallel connection of the first reactive branch and the first load, and a fourth reactive branch in series with the parallel connection of the second reactive branch and the second load, wherein a node is formed at a point between the third and fourth reactive branches, wherein the reactances of the third and fourth reactive branches are substantially equal in magnitude and opposite in sign at the first frequency.
23. The method according to claim 21 , further including coupling a first terminal of the first reactive branch and a first terminal of the first load to a first terminal of the input port, coupling a first terminal of the second reactive branch and a first terminal of the second load to a second terminal of the input port, and coupling together a second terminal of the first reactive branch, a second terminal of the first load, a second terminal of the second reactive branch and a second terminal of the second load.
24. A circuit, comprising: first and second loads having equivalent resistances at a first frequency that vary in a substantially identical fashion over a range of at least 2:1;and a resistance compression network having an input port and first and second output ports, the first output port to drive the first load and the second output port to drive the second load, the first input port having an input impedance at the first frequency that varies a first amount as impedances of the first and second loads vary substantially together by a second amount that is greater than the first amount.
25. The circuit of claim 24 , wherein power delivered to the input port of the resistance compression network is substantially losslessly transferred to the first and second loads.
26. The circuit according to claim 24 , wherein the first load includes a rectifier.
27. The circuit according to claim 24 , further including an inverter coupled to the compression network.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
May 3, 2006
May 19, 2009
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